Standard H264 provides two types of compression, illustrated in FIG. 1. A first compression type 100, known as lossless compression mode or lossless compression, obtains, from an original image 103, a restored image 104 after a compression phase 105 that does not lead to any loss in the restored image 104. A second type of compression 101, known as lossy compression mode or lossy compression, obtains, from an original image 106, a restored image 107 after a compression phase 108 that leads to a loss of data in the restored image 107 with relation to the original image 106, a data loss that manifests in a reduction in image quality, notably in terms of sharpness.
Standard H264 is preferred for the transmission of video across the network created. But this standard is, as explained previously, likely to produce data losses during compression operations occurring during video data encoding, in particular. Basically, these losses are considered to be not really discernable to the human eye; this was the case, in particular, when the video data to be encoded and transmitted were only of the photo or television broadcast image types, for example. However, in some cases, the defects introduced by these data losses may become very visible. This is the case in particular with images such as buttons, menus, or any other element containing text and many details.
More generally, when an image is compressed to gain transmission time or storage space, a certain loss rate is made in order to obtain a better compression rate. Such being the case, these losses, which do not pose problems for video visualization, are an inconvenience for image renderings of the graphic MMI type. In fact, more particularly, MMI renderings must be produced more carefully since the image is very often static or slightly animated, and the defects therein are perceptible. On the other hand, when an end user passes from a PC type station to an application on the television, his assessment of the identical content is more critical.